Indoor Air Quality
Indoor Air Quality, or IAQ, refers to the study, monitoring, remediation, and prevention of indoor air pollution and particles that cause discomfort and even health problems in homes and businesses. In the 1980’s and 1990’s Sick Building Syndrome became a popular term in the media because buildings and residences were beginning to be sealed tighter with less exchanges of fresh air. As a result, indoor air quality has become more important now than ever before. In the U.S. indoor air quality is regulated by the EPA and OSHA, as well as individual state regulations particularly in California, New Jersey, and Washington.
This is a comprehensive guide to IAQ procedures, problems, and measurement from TSI/Alnor. It is the best IAQ resource we have found. Click the image to download the PDF file.
![IAQ_handbook]()
Indoor air quality (IAQ) is generally broken up into two categories: comfort and health. Comfort concerns air temperature, humidity, and air velocity. However comfort is a subjective issue and as such it is impossible to please everyone in a building. It is more important to please the majority when it comes to comfortable indoor air so that productivity and concentration are maximized. An Indoor Air Quality Monitor is the tool needed to measure comfort parameters.
Health issues on the other hand are more serious. Although every person will be affected differently, higher than normal concentrations of certain harmful or irritating substances in the air can have potentially serious, even life threatening consequences. A particle counter is neccessary for measuring the concentration of these substances. In terms of health, poor IAQ is typically tied to symptoms like headaches, fatigue, and irritation of the eyes, nose, throat and lungs. Also, certain diseases like asthma have been linked to specific air contaminants or damp indoor environments.
Possible causes of IAQ problems:
- High or low humidity
- Air velocity too high/low
- Uncomfortable air temperature
- Activities in or near a building that can affect the incoming fresh air
- Dust from construction or renovation
- Mold
- Cleaning supplies
- Airborne chemicals including small amounts released over time from building materials, pesticides, volatile organic compounds (VOC), carbon monoxide, and improper exhaust ventilation of ozone (byproduct of some office machinery)
At TEquipment we offer products to monitor for these problems.
Indoor Air Quality Testing
Particle Counters
Particle counters detect and count particles in the air. Not only are they useful in HVAC applications for determining possible air contamination, but also for clean room environments where particles can adversely affect research or manufacturing. There are several types of particle counters but the two most popular today are Condensation Particle Counters and Optical Particle Counters. Condensation type particle counters (also referred to as "ultrafine particle counters") are able to detect smaller particles than any other type because they are capable of enlarging extremely small particles so they can be counted via conventional methods. Optical type particle counters use light and its reflection, refraction, and diffraction off of particles to count and determine size simultaneously. As such these instruments are more versatile. Optical particle counters also feature a larger particle size range than condesation type instruments.
There are two main factors that affect the choice of a particle counter:
As mentioned above, Condensation type particle counters are able to count particles smaller than the particles any other type of particle counter can handle. The drawbacks to this are that these units do not measure particle size and are only capable of counting a relatively small size range of particles. Typically this ranges from about 0.02 to 1.0 μm. Optical particle counters do measure particle size and are typically capable of counting particles ranging in size from about 0.3 to 25 μm.
The flow rate capability of a particle counter dictates how long you must sample air to meet specific requirements for particle concentration.
You can calculate this via this formula: Vs = (20/Cnm) x 1000
This formula will calculate how many litres of air need to be sampled at each location in a cleanroom. Take for example the certification of an ISO class 6 cleanroom. The largest considered particle size for this class is 5.0μm of which the cleanroom must have less than 293 particles per m3 (see table below). So our formula will look like this:
Vs = (20/293) x 1000 = 68.3
At each measuring point, 68.3 litres of air must be sampled. If a small handheld particle counter with a flow rate of 2 litres per minute is used, air will have to be sampled for 34.2 minutes at each measuring point. In this case it may be more economical to use a particle counter with a faster flow rate, minimize the time spent certifying the cleanroom.
| |
Particle Size per m3 |
ISO 15644-1
Cleanroom
Class |
U.S. STD 209E Cleanroom Class |
0.1 µm |
0.2 µm |
0.3 µm |
0.5 µm |
1.0 µm |
5.0 µm |
| 1 |
- |
10 |
2 |
- |
- |
- |
- |
| 2 |
- |
100 |
24 |
10 |
4 |
- |
- |
| 3 |
1 |
1,000 |
237 |
102 |
35 |
8 |
- |
| 4 |
10 |
10,000 |
2,370 |
1,020 |
352 |
83 |
- |
| 5 |
100 |
100,000 |
23,700 |
10,200 |
3,520 |
832 |
29 |
| 6 |
1,000 |
1,000,000 |
237,000 |
102,000 |
35,200 |
8,320 |
293 |
| 7 |
10,000 |
- |
- |
- |
352,000 |
83,200 |
2,930 |
| 8 |
100,000 |
- |
- |
- |
3,520,000 |
832,000 |
29,300 |
| 9 |
- |
- |
- |
- |
35,200,000 |
8,320,000 |
293,000 |
**Beyond these basic functions, some particle counters have additional features such as pre-programmed ISO formulas and options to measure airflow, temperature, and relative humidity.
Indoor Air Quality Monitors
Indoor Air Quality Monitors are portable or fixed instruments that measure multiple indoor air quality parameters. The parameters that can be measured vary by instrument, but most instruments concern the comfort aspect of IAQ. For example, the majority of these instruments measure humidity and temperature. Indoor air temperature may not be comfortable, and as a result building occupants may become irritable and less productive. If humidity is either low or high people will sense that their skin feels dry or think it feels “sticky,” resulting in decreased concentration on whatever task is at hand. Many of these units also address the health issues of IAQ.
Many of these instruments also incorporate data logging features with the option to export data to a PC. It is also important to note if an instrument comes factory calibrated or not. Some instruments do not come with calibration
Some examples of parameters:
- Carbon Monoxide (CO)
- Carbon Dioxide (CO2)
- Air velocity
- Temperature
- Humidity
- Volatile Organic Compounds (VOC's) such as Formaldehyde, Toluene and others found in many solvents and cleaners
- Combustion gases such as NO2, SO2, H2S